25.09.2020 23:32, Eric Blake wrote:
Allow the server to expose an additional metacontext to be requested
by savvy clients. qemu-nbd adds a new option -A to expose the
qemu:allocation-depth metacontext through NBD_CMD_BLOCK_STATUS; this
can also be set via QMP when using nbd-server-add.
qemu as client can be hacked into viewing this new context by using
the now-misnamed x-dirty-bitmap option when creating an NBD blockdev;
may be rename it to x-block-status ?
although it is worth noting the decoding of how such context
information will appear in 'qemu-img map --output=json':
NBD_STATE_DEPTH_UNALLOC => "zero":false, "data":true
NBD_STATE_DEPTH_LOCAL => "zero":false, "data":false
NBD_STATE_DEPTH_BACKING => "zero":true, "data":true
It wouldn't be so simple if we decide to export exact depth number..
--
Best regards,
Vladimir
